There are numerous circumstances in which longitudinal rails and their supports need to be tolerant of varying degrees of curvature in the vertical or horizontal plane. Herein, references to curvature in the vertical or horizontal plane are to curvature along the length of a rail.
A common circumstance in which there is such curvature of a rail is in a railway bridge joint. In a typical railway bridge joint, the rails on either side of the joint are rigidly attached to supports but a degree of relative rotational movement between the supports is permitted over time, for example as a consequence of thermal expansion and contraction of the bridge structure. Relative rotational movement between the supports may, for example, amount to 2.5 degrees or more of angular misalignment. This misalignment between the supports necessitates curvature in the portions of the rails which are arranged between the supports.
A number of support arrangements for rails having curvature in the vertical plane are known. A known support arrangement comprises a plurality of hinged support elements which serve to divide an angle between the end supports into smaller segments to reduce the impact at the end of each segment. Other known arrangements involve the provision of sprung and/or damped supports along the rail which allow the rail to bend while resisting large deflections caused by railway vehicle loads.
A problem associated with the known arrangements for supporting rails having curvature in the vertical plane is that none provides a rail having smooth curvature in the vertical plane and an appropriate level of compliance under different loadings. Embodiments of the invention seek to reduce or alleviate this problem. Embodiments of the invention may also address a corresponding problem associated with arrangements for supporting rails having curvature in the horizontal plane, such as may be used for directional control of vehicles.